The invention relates to insulating structures which are particularly adapted for use in electrostatic precipitators which are also known as scrubbers. While having particular application to use in electrostatic precipitators utilized in sulphuric acid plants, it will be understood that it also has application to other electrostatic precipitators and other apparatus.
Sulphuric acid does not occur as a free acid in nature. Most sulphuric acid is produced by a contact process which has the advantage that the acid can be obtained in any desired concentration. In the contact process, sulphur dioxide and other gases are obtained by roasting iron pyrites in a kiln. Dust in the gases is removed in electrostatic precipitators.
The basic operating principle of the electrostatic precipitator is demonstrated by the familiar experiment in which a glass rod is rubbed with a silk cloth. The rod is thereby given an electrostatic charge, making it capable of attracting uncharged bits of paper, lint, or cork. In the electrostatic precipitator, it is the collecting surfaces that are grounded, while a charge is created on the particles which are to be collected.
The power supply in such apparatus typically steps up line voltage and rectifies it to produce 50,000 volts of direct current. The direct current voltage is applied to a plurality of discharge electrode wires suspended in the gas flow path. The high potential on the discharge electrodes causes a corona discharge, from which electrons migrate out into the gas. These create gas ions, which attach themselves to particles in the gas and give the particles a charge.
Grounded collecting electrodes are also provided. The high potential difference results in a powerful electric field through which the gas is directed. In accordance with Coulomb's law, the field exerts a force on a charged particle in the field. This force moves particles out of the gas stream to the collecting electrodes. At the grounded collecting electrodes, the particles lose their charge. If the particles are in the form of dust, they are typically urged by gravity to a collecting area.
A problem associated with electrostatic precipitators of known construction is that the mounting of the electrodes does not adequately insure that arcing does not occur between the discharge and collecting electrodes and between various other elements. This arcing deteriorates the lead covered discharge electrodes and most importantly decreases the effectiveness of the electrostatic precipitator. The decrease in efficiency of such apparatus typically is in the order of 25% or more between annual service procedures. The inadequate relative positioning of the electrodes also results in major shutdowns of associated process apparatus. Because of environmental regulations, the shutdown of electrostatic precipitators will also necessarily result in the shutdown of all process equipment associated therewith. Such shutdowns frequently require the replacement of numerous components and substantial labor expense. The labor expense is particularly significant since the work is highly specialized and ordinarily requires outside technicians who may not be able to schedule their repair work promptly.
It is an object of the invention to provide apparatus which will more precisely orient the discharge and collecting electrodes to minimize arcing, down time and repairs, and to maximize efficiency of such electrostatic precipitators.
It is another object of the invention to provide apparatus which may be very inexpensively manufactured with manufacturing techniques which will utilize known plastic molding techniques.
Another object of the invention is to provide an insulating structure which may be easily installed on existing electrostatic precipitators.